Picornaviruses are viruses that belong to the family Picornaviridae. The name picornavirus means small RNA virus. Picornaviruses are non-enveloped, positive-stranded RNA viruses with an icosahedral capsid. The genome RNA is unusual because it has a protein on the 5' end that is used as a primer for transcription by RNA polymerase.

According to a study at the Mayo Clinic, picornaviruses can "cross over" into the brain, causing memory loss and other neurological symptoms.

Picornaviruses include two main categories: the enteroviruses and the rhinoviruses. Some important enteroviruses are poliovirus and Hepatitis A virus. Enteroviruses infect the enteric tract as it is visible from its name. On the other hand, Rhinoviruses infect primarily the nose and the throat. Enteroviruses replicate at 37°C, whereas Rhinoviruses grow better at 33°C, as this is the lower temperature of the nose. Enteroviruses are stable under acid conditions and thus they are able to survive exposure to gastric acid. In contrast, Rhinoviruses are acid-labile and that is the reason why Rhinoviruses are restricted to the nose and throat.

HANOI - A SURGING outbreak of hand, foot and mouth disease has killed 70 people so far this year in Vietnam and infected more than 23,000, mostly children under 5, state-controlled media reported on Thursday.

Most of the cases have been reported in the country's south, and enterovirus 71, or EV-71, is the dominant strain circulating in Vietnam, Nguyen Van Binh, head of the Ministry of Health's Department of Preventive Medicine, was quoted by Thanh Nien newspaper as saying.

EV-71 can result in a more serious form of the common childhood disease leading to paralysis, brain swelling or death.

This year's outbreak is a sharp uptick from recent years. Since 2008, about 10,000 to 15,000 cases were reported per year with about 20 to 30 children dying annually.

Mr Binh said the virus has appeared to slow in recent weeks, but the rate remains high with up to 1,900 new cases reported each week.

He warned there could be more new cases when children return to school in early September. The virus is easily spread by sneezing and coughing. -- AP